From 00ea0b1d57a7ae775df81d0913af7905f7d76e32 Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Sat, 10 Jul 2021 23:15:58 +0200
Subject: [PATCH] build: list libraries at the end of the linker command

Static libraries should be added at the end of the linker command, after
all object files. If that isn't done, that's _usually_ not a problem,
unless there are duplicate symbols. In that case, weird dependency
issues can arise. To solve that, object files (that may include symbols
to override symbols in the library) should be listed first on the
command line and then the static libraries should be listed.

This fixes an issue with overriding some symbols in wasi-libc.
---
 builder/build.go | 50 +++++++++++++++++++++++++-----------------------
 1 file changed, 26 insertions(+), 24 deletions(-)

diff --git a/builder/build.go b/builder/build.go
index f17d26c7..5c38433b 100644
--- a/builder/build.go
+++ b/builder/build.go
@@ -470,33 +470,10 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 		linkerDependencies = append(linkerDependencies, job)
 	}
 
-	// Add libc dependency if needed.
-	root := goenv.Get("TINYGOROOT")
-	switch config.Target.Libc {
-	case "picolibc":
-		job, err := Picolibc.load(config.Triple(), config.CPU(), dir)
-		if err != nil {
-			return err
-		}
-		// The library needs to be compiled (cache miss).
-		jobs = append(jobs, job.dependencies...)
-		jobs = append(jobs, job)
-		linkerDependencies = append(linkerDependencies, job)
-	case "wasi-libc":
-		path := filepath.Join(root, "lib/wasi-libc/sysroot/lib/wasm32-wasi/libc.a")
-		if _, err := os.Stat(path); os.IsNotExist(err) {
-			return errors.New("could not find wasi-libc, perhaps you need to run `make wasi-libc`?")
-		}
-		ldflags = append(ldflags, path)
-	case "":
-		// no library specified, so nothing to do
-	default:
-		return fmt.Errorf("unknown libc: %s", config.Target.Libc)
-	}
-
 	// Add jobs to compile extra files. These files are in C or assembly and
 	// contain things like the interrupt vector table and low level operations
 	// such as stack switching.
+	root := goenv.Get("TINYGOROOT")
 	for _, path := range config.ExtraFiles() {
 		abspath := filepath.Join(root, path)
 		job := &compileJob{
@@ -537,6 +514,31 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 		ldflags = append(ldflags, lprogram.LDFlags...)
 	}
 
+	// Add libc dependency if needed.
+	switch config.Target.Libc {
+	case "picolibc":
+		job, err := Picolibc.load(config.Triple(), config.CPU(), dir)
+		if err != nil {
+			return err
+		}
+		// The library needs to be compiled (cache miss).
+		jobs = append(jobs, job.dependencies...)
+		jobs = append(jobs, job)
+		linkerDependencies = append(linkerDependencies, job)
+	case "wasi-libc":
+		path := filepath.Join(root, "lib/wasi-libc/sysroot/lib/wasm32-wasi/libc.a")
+		if _, err := os.Stat(path); os.IsNotExist(err) {
+			return errors.New("could not find wasi-libc, perhaps you need to run `make wasi-libc`?")
+		}
+		job := dummyCompileJob(path)
+		jobs = append(jobs, job)
+		linkerDependencies = append(linkerDependencies, job)
+	case "":
+		// no library specified, so nothing to do
+	default:
+		return fmt.Errorf("unknown libc: %s", config.Target.Libc)
+	}
+
 	// Create a linker job, which links all object files together and does some
 	// extra stuff that can only be done after linking.
 	jobs = append(jobs, &compileJob{